Strange brake problems - about to sell the P.O.S. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tekno62 · 03-18-2010, 08:48 PM

Need brake help – so far I have replaced the master cylinder 3 times and the combo valve once but still have the same problem. After just a few weeks the master cylinder “O”rings go bad eaten up by something.

What else could be killing my brakes.

SCOTI · 03-18-2010, 10:59 PM

Replaced the master cyl 3x from different suppliers or the same supplier?
Type of fluid?

tekno62 · 03-18-2010, 11:20 PM

from Kragen - the first one was new ( not remaned ) the next 2 where remaned and 2 where different the fluid was type 3 or 5 cant remember.

Quote:

Originally Posted by SCOTI

Replaced the master cyl 3x from different suppliers or the same supplier?
Type of fluid?

SCOTI · 03-19-2010, 12:05 AM

Quote:

Originally Posted by tekno62

from Kragen - the first one was new ( not remaned ) the next 2 where remaned and 2 where different the fluid was type 3 or 5 cant remember.

I like using Raybestos or Wagner master cylinders. Is Kragens their 'name' stuff or possibly one of those?

I know some fluids require spec'd seals & such. Verify what fluid your using.

chevyrestoguy · 03-19-2010, 03:51 PM

Sounds like you're using Dot 5 fluid. That stuff is not compatible with some seals and will eat them up over time.

Just use Dot 3. It's non-synthetic and it's a lot more forgiving.

cparman · 03-19-2010, 09:43 PM

been beat up a few times with DOT 4 or5 I use Dot 3 only. The bad experiences I have had with DOT 5 is a mushy pedal, but after getting the brakes hot the pedal comes back.

Quote:

Originally Posted by chevyrestoguy

Sounds like you're using Dot 5 fluid. That stuff is not compatible with some seals and will eat them up over time.

Just use Dot 4. It's non-synthetic and it's a lot more forgiving.

tekno62 · 03-20-2010, 08:23 PM

using dot 3 - going to rebead with new master and see

dznucks · 03-22-2010, 08:47 AM

I had similar problems awhile back. the DOT 4 & 5 stuff will eat up alot of rubber seals and hoses if they are not compatible. especially in these older vehicles that still have parts that were made berfore these types of brake fluids existed.

also some of these fluids are not compatible together. If you change types of fluids without completely flushing the system, air bubbles will form and stay suspended. this causes the mushy pedal.

If you are unsure, I would flush the system completely and refill with new DOT 3. stay away from synthetic too, unless you upgrade to a system that requires it.

bedsled71 · 03-22-2010, 09:58 AM

ive never heard of anyone useing something other than dot3 for these brakes

03-18-2010, 08:48 PM	#1
tekno62 Registered User Join Date: Nov 2008 Location: San Jose Ca Posts: 265	Strange brake problems - about to sell the P.O.S. Need brake help – so far I have replaced the master cylinder 3 times and the combo valve once but still have the same problem. After just a few weeks the master cylinder “O”rings go bad eaten up by something. What else could be killing my brakes. Last edited by tekno62; 03-18-2010 at 08:49 PM. Reason: cant spell

03-18-2010, 10:59 PM	#2
SCOTI Registered User Join Date: Apr 2001 Location: DALLAS,TX Posts: 22,132	Re: Strange brake problems - about to sell the P.O.S. Replaced the master cyl 3x from different suppliers or the same supplier? Type of fluid? __________________ 67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... *Cubic inches is like Indiana Jones with a cheap pistol.*

03-19-2010, 03:51 PM	#5
chevyrestoguy Registered User Join Date: Mar 2005 Location: apple valley, ca Posts: 2,670	Re: Strange brake problems - about to sell the P.O.S. Sounds like you're using Dot 5 fluid. That stuff is not compatible with some seals and will eat them up over time. Just use Dot 3. It's non-synthetic and it's a lot more forgiving. Last edited by chevyrestoguy; 03-23-2010 at 10:42 AM.

03-20-2010, 08:23 PM	#7
tekno62 Registered User Join Date: Nov 2008 Location: San Jose Ca Posts: 265	Re: Strange brake problems - about to sell the P.O.S. using dot 3 - going to rebead with new master and see

03-22-2010, 08:47 AM	#8
dznucks Registered User Join Date: Feb 2006 Location: Smyrna, Ga Posts: 1,647	Re: Strange brake problems - about to sell the P.O.S. I had similar problems awhile back. the DOT 4 & 5 stuff will eat up alot of rubber seals and hoses if they are not compatible. especially in these older vehicles that still have parts that were made berfore these types of brake fluids existed. also some of these fluids are not compatible together. If you change types of fluids without completely flushing the system, air bubbles will form and stay suspended. this causes the mushy pedal. If you are unsure, I would flush the system completely and refill with new DOT 3. stay away from synthetic too, unless you upgrade to a system that requires it.

03-22-2010, 09:58 AM	#9
bedsled71 Registered User Join Date: Feb 2007 Location: yuma arizona Posts: 448	Re: Strange brake problems - about to sell the P.O.S. ive never heard of anyone useing something other than dot3 for these brakes



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